We report the production of matter-wave solitons in an ultracold lithium-7 gas. The effective interaction between atoms in a Bose-Einstein condensate is tuned with a Feshbach resonance from repulsive to attractive before release in a one-dimensional optical waveguide. Propagation of the soliton without dispersion over a macroscopic distance of 1.1 millimeter is observed. A simple theoretical model explains the stability region of the soliton. These matter-wave solitons open possibilities for future applications in coherent atom optics, atom interferometry, and atom transport.

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We present release 2.0 of the ALPS (Algorithms and Libraries for Physics Simulations) project, an open source software project to develop libraries and application programs for the simulation of strongly correlated quantum lattice models such as quantum magnets, lattice bosons, and strongly correlated fermion systems. The code development is centered on common XML and HDF5 data formats, libraries to simplify and speed up code development, common evaluation and plotting tools, and simulation programs. The programs enable non-experts to start carrying out serial or parallel numerical simulations by providing basic implementations of the important algorithms for quantum lattice models: classical and quantum Monte Carlo (QMC) using non-local updates, extended ensemble simulations, exact and full diagonalization (ED), the density matrix renormalization group (DMRG) both in a static version and a dynamic time-evolving block decimation (TEBD) code, and quantum Monte Carlo solvers for dynamical mean field theory (DMFT). The ALPS libraries provide a powerful framework for programers to develop their own applications, which, for instance, greatly simplify the steps of porting a serial code onto a parallel, distributed memory machine. Major changes in release 2.0 include the use of HDF5 for binary data, evaluation tools in Python, support for the Windows operating system, the use of CMake as build system and binary installation packages for Mac OS X and Windows, and integration with the VisTrails workflow provenance tool. The software is available from our web server at http://alps.comp-phys.org/.

We present a new family of stationary solutions to the cubic nonlinear Schrödinger equation with a Jacobian elliptic function potential. In the limit of a sinusoidal potential our solutions model a dilute gas Bose-Einstein condensate trapped in a standing light wave. Provided the ratio of the height of the variations of the condensate to its DC offset is small enough, both trivial phase and nontrivial phase solutions are shown to be stable. Numerical simulations suggest such stationary states are experimentally observable.The dilute-gas Bose-Einstein condesate (BEC) in the quasi-one-dimensional regime is modeled by the cubic nonlinear Schrödinger equation (NLS) with a potential [1][2][3]. The various traps which are used to contain the BEC have spurred the solution of the NLS with new potentials [4,5]. BECs trapped in a standing light wave have been used to study phase coherence [6] and matter-wave diffraction [7] and have been predicted to have applications in quantum logic [8] and matter-wave transport [9]. Exact solutions have been obtained for the Kronig-Penney potential [10] and some researchers have used a Bloch function description [11]. In this letter, we study new explicit solutions of the NLS with a Jacobian elliptic function potential.We consider the mean-field model of a quasi-onedimensional repulsive BEC trapped in an external potential which is given by the nonlinear Schrödinger equation [1]In experiments, the trapping potential is generated by a standing light wave [6]. As a model for such a potential we use the periodic potentialwhere sn(x, k) denotes the Jacobian elliptic sine function [12] with elliptic modulus 0 ≤ k ≤ 1. In the limit k → 1 − , V (x) becomes an array of well-separated hyperbolic secant potential barriers or wells, while in the limit k → 0 + it becomes purely sinusoidal. We note that for intermediate values (e.g. k = 1/2) the potential closely resembles the sinusoidal behavior and thus provides a good approximation to the standing wave potential generated experimentally [6]. We present stationary solutions in closed form and study their stability analytically and numerically. We begin by constructing solutions to Eq. (1) which have the formwherewhere B determines a mean amplitude and acts as a DC offset for the number of condensed atoms. The strength of the nonlinearity, which for the BEC is a function of both the atomic coupling and the number of condensed atoms, is determined by the parameters V 0 + k 2 and B, as is apparent in the amplitude of the solutions given by Eq. (3). Note that if x is scaled so that V (x) undergoes only a single oscillation on the ring (in the limit k → 1) the Jacobian elliptic potential provides a model of a single barrier or well [13]. For simplicity we focus on two special cases: (1) k arbitrary and trivial phase (c = 0), and (2) k = 0 with nontrivial phase (c = 0) so that the solutions are trigonometric functions. Trivial Phase Case -In the limit of c = 0, the solutions given in Eqs. (3)-(4) reduce tovalid for V 0 ≥ −k 2 , and ψ(x, t) = −(V 0 +k 2...

We present a new way of nanoengineering graphene by using defect domains. These regions have ring structures that depart from the usual honeycomb lattice, though each carbon atom still has three nearest neighbors. A set of stable domain structures is identified by using density functional theory, including blisters, ridges, ribbons, and metacrystals. All such structures are made solely out of carbon; the smallest encompasses just 16 atoms. Blisters, ridges, and metacrystals rise up out of the sheet, while ribbons remain flat. In the vicinity of vacancies, the reaction barriers to formation are sufficiently low that such defects could be synthesized through the thermally activated restructuring of coalesced adatoms.

The stability regimes and nonlinear dynamics of bright solitons created in a harmonic potential which is transversely attractive and longitudinally expulsive are presented. This choice of potential is motivated by the recent creation of a matter-wave bright soliton from an attractive Bose-Einstein condensate (L. Khaykovich {\it et al.}, Science 296, 1290 (2002)). The critical branches for collapse due to the three-dimensional character of the gas and explosion caused by the expulsive potential are derived based on variational studies. Particle loss from the soliton due to sudden changes in the trapping potential and scattering length are quantified. It is shown that higher order solitons can also be created in present experiments by an abrupt change of a factor of four in the scattering length. It is demonstrated that quantum evaporation occurs by nonlinear tunneling of particles out of the soliton, leading eventually to its explosion.Comment: 11 pages, 6 figure

Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical, and that do not have a simple description in terms of weakly interacting quasi-particles. Two systems that have recently attracted a great deal of interest are the quark-gluon plasma, a plasma of strongly interacting quarks and gluons produced in relativistic heavy ion collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic gases confined in optical or magnetic traps. These systems differ by more than 20 orders of magnitude in temperature, but they were shown to exhibit very similar hydrodynamic flow. In particular, both fluids exhibit a robustly low shear viscosity to entropy density ratio which is characteristic of quantum fluids described by holographic duality, a mapping from strongly correlated quantum field theories to weakly curved higher dimensional classical gravity. This review explores the connection between these fields,

All stationary solutions to the one-dimensional nonlinear Schrödinger equation under box or periodic boundary conditions are presented in analytic form for the case of attractive nonlinearity. A companion paper has treated the repulsive case. Our solutions take the form of bounded, quantized, stationary trains of bright solitons. Among them are two uniquely nonlinear classes of nodeless solutions, whose properties and physical meaning are discussed in detail. The full set of symmetry-breaking stationary states are described by the Cn character tables from the theory of point groups. We make experimental predictions for the Bose-Einstein condensate and show that, though these are the analog of some of the simplest problems in linear quantum mechanics, nonlinearity introduces new and surprising phenomena.